The present invention relates to a method and apparatus for video signal processing. More particularly, it relates to assuring video signal format integrity for the recording, transmission and viewing of a video signal by reestablishing proper video AGC and sync parameters.
Various methods and apparatus have been developed and incorporated for modifying a video signal by the introduction and/or replacement of sync pulses in a manner to allow normal viewing by a television receiver, but preventing the making of a recording acceptable for viewing. U.S. Pat. No. 4,100,575 entitled “METHOD AND APPARATUS FOR MODIFYING A VIDEO SIGNAL TO PREVENT UNAUTHORIZED RECORDING AND REPRODUCTION THEREOF” which issued on Jul. 11, 1978 to Minoru Morio et al discloses a process of replacing a portion of vertical pulses with equalizing pulses in some of the vertical blanking intervals. U.S. Pat. No. 4,631,603 entitled “METHOD AND APPARATUS FOR PROCESSING VIDEO SIGNALS SO AS TO PROHIBIT THE MAKING OF ACCEPTABLE VIDEO TAPE RECORDINGS” which issued on Dec. 23, 1986 to John O. Ryan discloses a process by which ordered pairs of pseudo-sync pulses and white pulses are added during the vertical blanking intervals and interfere with a VCR's recording and AGC circuitry. The white or positive pulses would correspond to incorrect AGC levels. U.S. Pat. No. 4,819,098 entitled “METHOD AND APPARATUS FOR CLUSTERING MODIFICATIONS MADE TO A VIDEO SIGNAL TO INHIBIT THE MAKING OF ACCEPTABLE VIDEOTAPE RECORDINGS” which issued on Apr. 4, 1989 to John O. Ryan discloses another method and apparatus for adding a plurality of positive pulses to the video signal with each immediately following a respective trailing edge of a normally occurring sync pulse. These added pulses are clustered at the vertical blanking interval of each field and interferes with the automatic level control circuit of a recording device. U.S. Pat. No. 6,836,549 B1 entitled “METHOD AND APPARATUS FOR SYNTHESIZING AND REDUCING THE EFFECTS OF VIDEO COPY PROTECTION SIGNALS” which was issued on Dec. 28, 2004 to Ronald Quan et al discloses a method and apparatus for defeating copy protection signals in a video signal, and also for providing copy protection signals for a video signal. The defeat method generally utilizes a particular pulse position shifting, modulation, etc., of AGC, normal sync and/or pseudo sync pulses to increase the separation between the pulses and the copy protection method includes various embodiments for dynamically varying the sync/pseudo sync and AGC separation. U.S. Pat. No. 7,087,380 B2 entitled “METHOD FOR MODIFYING A COPY PROTECTED VIDEO SIGNAL WITH A NEGATIVE AMPLITUDE PULSE” issued on Aug. 1, 2006 to Ronald Quan discloses an enhancement to existing copy protected signals by the addition of negative amplitude pulses to the video signal at a location in the horizontal blanking interval “back porch” after the color burst.
There are methods and apparatus that have been developed and incorporated for detection and subsequent neutralization of these video signal modifications. U.S. Pat. No. 4,695,901 entitled “METHOD AND APPARATUS FOR REMOVING PSEUDO-SYNC AND/OR AGC PULSES FROM A VIDEO SIGNAL” which issued on Sep. 22, 1987 to John O. Ryan discloses a selectively-operable clipping circuit used to remove pseudo-sync pulses from a video signal, while added AGC pulses are effectively blanked from a video signal with an electrically-operable switch. U.S. Pat. No. 5,157,510 entitled “METHOD AND APPARATUS FOR DISABLING ANTI-COPY PROTECTION SYSTEM IN VIDEO SIGNALS USING PULSE NARROWING” which issued on Oct. 20, 1992 to Ronald Quan discloses a method and apparatus that effectively increases the high-frequency content of the pseudo-sync and/or AGC pulses. This renders the pulses susceptible to attenuation and/or low-pass filtering in the VCR circuitry to counteract the effectiveness of the pulses in preventing copying. U.S. Pat. No. 5,194,965 entitled “METHOD AND APPARATUS FOR DISABLING ANTI-COPY PROTECTION SYSTEM IN VIDEO SIGNALS” which issued on Mar. 16, 1993 to Ronald Quan et al discloses a method and apparatus for altering the level of the video signal during the vertical blanking interval, e.g., level-shifting, so as to render the copy-protect signals ineffective to prevent unauthorized copying by a VCR. An alternative method includes increasing the effective frequency of the copy-protect signals during the vertical blanking interval so as to achieve attenuation and/or low-pass filtering in the VCR circuitry to counteract the effectiveness of the signals in preventing copying. U.S. Pat. No. 5,625,691 entitled “METHOD AND APPARATUS TO DEFEAT CERTAIN COPY PROTECTION PULSES WITHIN A VIDEO SIGNAL” which issued on Apr. 29, 1997 to Ronald Quan, U.S. Pat. No. 5,633,927 entitled “VIDEO COPY PROTECTION PROCESS ENHANCEMENT TO INTRODUCE HORIZONTAL AND VERTICAL PICTURE DISTORTIONS” which issued on May 27, 1997 to John O. Ryan et al and U.S. Pat. No. 5,748,733 entitled “METHOD AND APPARATUS TO REDUCE THE EFFECTS OF CERTAIN COPY PROTECTION PURSES WITHIN A VIDEO SIGNAL” which issued on May 5, 1998 to Ronald Quan each disclose several modifications to a video signal that are added to the existing basic anti-copy signals of pseudo-sync and/or AGC pulses thus the enhancement of the anti-copy system. One of these enhancements involves the introduction of signals into the overscan portion of the video signal in order to trigger an early horizontal or vertical retrace. Another enhancement is the narrowing of selected horizontal sync signals. Others enhancements are also disclosed. Methods and apparatus to remove these enhancing modifications include level shifting and sync widening. U.S. Pat. No. 6,002,830 entitled “METHOD AND APPARATUS FOR REMOVING OR DEFEATING EFFECTS OF COPY PROTECTION SIGNALS FROM A VIDEO SIGNAL” which issued on Dec. 14, 1999 to Ronald Quan and U.S. Pat. No. 6,421,497 entitled “METHOD FOR LOCATING COPY PROTECTION PULSES WITHIN SELECTED VIDEO LINES OF A VIDEO SIGNAL” which issued on Jul. 16, 2002 to Ronald Quan each disclose a method and apparatus for detection of copy protection pulses using the color burst signal or chroma in the horizontal blanking interval then modifying the video signal so as to render it recordable. These modifications include gain-shifting portions of the video signal, level-shifting portions of the video signal, bandwidth limiting certain portions of the video signal or replacing certain portions of the video signal with other video elements. U.S. Pat. No. 6,501,842 B2 entitled “METHOD AND APPARATUS FOR MODIFYING A VIDEO SIGNAL BY BACK PORCH LOWERING” which issued on Dec. 31, 2002 to Ronald Quan discloses a method and apparatus that replaces or level shifts portions of a video signal to defeat the effects of copy protection signals.
Methods and apparatus have been developed to aid and/or impair the detection of synchronizing signals necessary for the reconstitution of altered video signals. U.S. Pat. No. 4,571,615 entitled “TIMING GENERATOR FOR SYNC SUPPRESSED TELEVISION SIGNALS” which issued Feb. 18, 1986 to Clyde Robbins et al discloses a device which detects the absence and the first reoccurrence of the color burst signal to generate a synchronizing signal. U.S. Pat. No. 4,684,988 entitled “CIRCUIT ARRANGEMENT FOR DETECTING THE VERTICAL BLANKING PERIODS IN A PICTURE SIGNAL” which was issued on Aug. 4, 1987 to Kurt J. Johannes discloses a circuit for detecting the blanking period in a picture signal, having a pulse interval detector and a subsequent pulse shaping stage. U.S. Pat. No. 5,034,981 entitled ‘ANTI-COPYING VIDEO SIGNAL PROCESSING” issued Jul. 23, 1991 to Eugene Leonard et al discloses a method and apparatus that disrupts digital vertical synchronizing circuit operation. U.S. Pat. No. 5,179,452 entitled “METHOD FOR PRODUCING COPY PROTECTED RECORDED VIDEOTAPE HAVING UNCOPYABLE VERTICAL SYNCHRONIZING SIGNAL PARTITION” which was issued Jan. 12, 1993 to Yasunori Takahashi disclose a method of altering the vertical sync pulses in order to disrupt the operation of a videotape recorder. U.S. Pat. No. 6,931,547 B2 entitled “METHOD AND APPARATUS FOR IDENTIFYING A VERTICAL BLANKING INTERVAL IN A TELEVISION SIGNAL” which was issued on Aug. 16, 2005 to Ronald Quan and the continuation of U.S. Pat. No. 6,931,547 B2 being, U.S. Pat. No. 7,100,209 B2 entitled “METHOD TO PROVIDE THE GENERATION OF AN INCORRECT OR UNRELIABLE VERTICAL/FRAME SIGNAL” which issued on Aug. 29, 2006 to Ronald Quan each disclose techniques for modifying the characteristic signals of the Vertical Blanking Interval (VBI) for the generation of an incorrect or unreliable vertical or frame rate signal, via particular characteristics and/or peculiarities of the signals in the VBI.
The aforementioned copy protection (CP) methods and apparatus and the complementary defeat methods and apparatus (anti-CP) are associated with any type of disruption of the synchronizing format of a video signal which requires unique circuit arrangements of commonly available analog circuits and/or digital circuits. Many of these circuits and sub-circuits are comprised of fixed components and hardwiring defining narrow operating characteristics and parameters thus limiting flexibility. A complete unified system that effectively encompasses CP methods and apparatus and/or anti-CP methods and apparatus using the same circuitry and sub-circuitry would be cumbersome and limited in operational flexibility. The generation of corrective sync signals is a part of a unified system. Methods and apparatus for generating television sync signals have also been devised. U.S. Pat. No. 4,169,659 entitled “MULTIPLE STANDARD TELEVISION SYNC GENERATOR’ which issued on Oct. 2, 1979 to Frank J. Marlowe discloses such an apparatus. This disclosure does not lend itself readily to the application of CP and/or anti-CP systems because it requires a particular synchronizing signal which limits its flexibility. The aforementioned apparatus cannot be programmed to respond to any selected event, such as sync pulses, other than synchronization during normal operation. The apparatus cannot be programmed to generate single pulse or partial pulse trains from selected outputs as required. The following brief summary of the present invention will clarify additional limitations and shortcomings of the entire aforementioned prior art.